A system for sealing a percutaneous puncture in a vessel can comprise an inner seal, which is adapted to be positioned against an inner surface of the vessel wall, and a locking member, which is connected to the inner seal by, for example, a filament or a suture and which is adapted to be positioned against an outer surface of the vessel wall, such that the percutaneous puncture is sealed there between. During the phase of inserting the inner seal, the inner seal is folded inside an insertion tube, resting in the puncture to provide access to the inner surface of the blood vessel. Deployment of the inner seal inside the vessel takes place by pushing the inner seal through the insertion tube, and out from its distal end opening. To ensure proper unfolding of the inner seal inside the vessel, the inner seal has to be Deployed some distance away from the puncture hole in the vessel wall before the inner seal is retracted to be securely seated against the inner surface of the vessel wall. When the inner seal has been deployed inside the blood vessel, the insertion tube is retracted out from the puncture, and in the same movement the inner seal is retracted and seated against the inner wall of the blood vessel. When the inner seal has been correctly positioned against the inner surface of the vessel wall, the locking member is pushed forward through the insertion tube until the locking member is in contact with the outer surface of the vessel wall. To effectuate the different actions described above, insertion tools have been proposed, which also accommodate the inner seal and the locking member before the sealing procedure.
As indicated, a critical moment in the above procedure is to ascertain a correct Positioning of the insertion tube before deployment of the inner seal. To achieve this there are various methods disclosed in the prior art. One method (see, e.g., U.S. Pat. No. 5,306,254) comprises making available a channel for blood to flow in through a distal opening in a dilator, inserted in an introducer sheath, via an opening or port located at a point on said introducer. There is also provided a proximal opening through which blood can flow out, whereby the occurrence or non-occurrence of outflow of blood indicates correct or incorrect position. Thereby, said port is located on the introducer sheath such that blood enters said port only when the tip of the introducer sheath is at a correct position. This method, although being relatively efficient, entails spillage of blood, which is inconvenient and may soil the environment around the patient to an undesirable extent.
In U.S. Pat. No. 5,295,969 there is disclosed a means for accessing blood vessels for the Insertion of a guide wire while preventing the free release of blood. Specifically, a hollow, thin-walled metal tube typically having a sharp point at its distal end is joined at its proximal end to a transparent viewing section. The viewing section has a distal narrow lumen and a proximal chamber which has a cap at its proximal end. The cap encloses a pressure sealing means through which a guide wire can be passed. After the distal end of the metal tube is placed in an artery, blood will rush through the metal tube and into the viewing section. The air in the air-tight proximal chamber will alternatively be compressed between diastolic and systolic blood pressure. Feedback to the operator that the distal end of the metal tube is properly placed within an artery can be achieved by observing the reciprocating pulsatile motion of the blood column within the distal narrow lumen of the viewing section. When the proper pulsatile motion is observed, a guide wire can be passed through the sealing means in the cap, through the viewing section, through the metal tube and finally the guide wire will enter the lumen of the artery.
However, a disadvantage with this device is that it will not be usable for all possible pressures that may be encountered. Namely, if blood enters the chamber the meniscus of blood will be located inside the chamber, and fluctuations may not readily be observed, either because the difference in levels between fluctuations is too small, or because the chamber simply cannot be observed.